The present invention relates generally to a magnetic sheet having two-dimensional alternating poles. Such magnetic sheets may be used in a wide range of applications, including shoe insoles for shoes that have magnetic particles embedded therein.
Insoles have generally been formed by a pad of cushioning material, such as sponge rubber, that has a general shape conforming to the interior of a shoe. Wearers who desire additional shoe comfort or who suffer from foot trouble, for example, plantar heel pain and/or arch pain, insert the cushioned insole into the shoe to provide added cushioning and support.
It is also known to provide insoles with magnetic particles therein. The magnetic particles are arranged in areas of alternating polarity. The reason for providing the magnetic particles is to increase blood flow and thereby accelerate healing of injured body parts. The basic theory is that charged particles in the blood stream, such as calcium ions, sodium chloride ions, electrolytes and the like, which are used for various purposes such as repairing bone and tissue, etc., are forced by the changing magnetic polarities through which the blood vessel passes, to move from one side of the blood vessel to the other side of the blood vessel as they travel along the blood vessel. This creates heat and helps to accelerate blood flow by bringing more blood to the blood vessel.
U.S. Pat. No. 4,489,711 to Latzke discloses the use of alternating stripes of unidirectional north and south magnetic poles. However, when the blood vessel extends in the same direction as the magnetic stripes, there is no alternating magnetic field, and no therapeutic effect. See also U.S. Pat. No. 5,233,768 to Humphreys for a similar disclosure.
U.S. Pat. No. 4,549,532 to Baermann discloses alternating magnetic areas formed as concentric rings or radial sectors. However, for blood vessels, which are positioned near the periphery of the concentric ring arrangement, the effect is less effective, since the blood vessel will traverse an area of only one polarity. The reverse is true for the radial sectors, since a blood vessel passing through the center will traverse only an area of only one polarity.
U.S. Pat. Nos. 5,277,692; 5,514,072; 5,538,495; and 5,871,438, all to Ardizzone, attempt to overcome the problems with the above patents. Specifically, Ardizzone provides a spiral arrangement of magnetic areas of alternating polarity, with the areas reducing in size toward the outside and inside of the spiral. This arrangement is provided to take into account all random positions of the blood vessels, to ensure that the blood vessels, regardless of orientation, always traverse alternating polarity areas. The problem arises, however, in the manufacture of this pattern. This is because of the complexity of the pattern, and the fact that it provides little tolerance for offsets during manufacturing. Thus, if there is any offset in the magnetic areas from the desired pattern, the position of entire pattern is thrown off.
The Ardizzone patents also provide an alternative checkerboard pattern of alternating polarity areas. Each area of one polarity is surrounded by either three or four areas of opposite polarity. However, with this arrangement, areas of opposite polarity contact each other at corner points to provide alternating zones of opposite polarity. This also provides little tolerance for variations in manufacture, and makes manufacture thereof extremely difficult.
U.S. Pat. No. 5,304,111 to Mitsuno et al discloses alternating sinusoidal areas of opposite polarity. However, when dealing with such sinusoidal patterns, it may be difficult to maintain an exact pitch of each boundary line relative to an adjacent boundary line, and an exact spacing between the boundary lines. Even with the exact arrangement of Mitsuno et al, the boundary lines come close to each other, and thereby come close to approximating the checkerboard pattern of the Ardizzone patents. Mitsuno et al also discloses a polka dot pattern. However, Mitsuno et al admits that a blood vessel can be aligned to run along only a zone of south polarity. In such case, even if a blood vessel overlies adjacent zones of alternating north and south polarity, the magnetic pull on opposite sides will be equal and cancel out, thereby having no affect on the charged particles in the blood vessel.
Other patents of interest are U.S. Pat. Nos. 4,033,054 (Fukuoka), 4,079,526 (Fukuoka), 4,109,661 (Fukuoka), 4,223,458 (Kihara), 4,270,966 (Kihara), 4,727,661 (Kuhn), 4,843,738 (Masuda), 5,553,398 (Schnewlin-Maier), 5,685,094 (Lin) and 5,738,624 (Zablotsky et al).
The entire disclosures of all of the aforementioned U.S. Patents are incorporated herein by references.